Remote relay control by radio



1954 J. J. HUPERT EI'AL REMOTE-RELAY CONTROL BY RADIO 2 Sheets-Sheet 1 Filed Nov. 29, 1949 IN V EN TOR-5 [Ha 04m idEZ'd/Z 1954 J. J. HUPERT arm.

REMOTERELAY CONTROL BY RADIO 2 Sheets-Sheet 2 Filed Nov. 29, 1949 INVENTORS (XE WW5? United States Patent "ice REMOTE RELAY CONTROL BY RADIO Julius J. Hupert, River Forest, and Richard Goldsteiu, Chicago, Ill., assignors to A. R. F. Products, lnc.,River "Forest, 111., acorporation of Illinois Application November 29, 1949, Serial No.-130,061

2 Claims. (Cl. 317-442) The present invention isa continuation-in-part of our application Serial No. 47,886, filed September 4, 1948, and entitled Remote Control Device, which is now abandoned, and relates to a remote control device, this device being primarily intended for opening a garage door from inside a'car, although the invention may be used for other purposes.

Various types of such remote control devices have been used in the past and have been found wanting. These devices include radio communication devices operating on conventional radio frequencies,-microwave devices, electromagnetic induction devices without an electronic amplifier, supersonic sound devices, audio sound devices, and photocell devices.

A radio communication device has the dual disadvantage of difficulties in complying with Federal Communications Commission regulations and of being particularly susceptible to electrical disturbances. Electronic devices for scientific, industrial and medical use, as well as other electrical disturbances, both natural and manmade, often cause the garage doors to open and close at random.

Microwave devices are generally not quite so susceptible to electrical disturbance as such disturbance is more common in the lowerranges of thefrequency spectrum, but these devices are expensive to manufacture. Occa- Sional long distance transmission phenomena which are quite unpredictable cause radio frequency energy to be transmitted abnormal distances and this .energy then opens the garage doors of other parties living at considerable distances but operating on the same frequency.

Previous electromagnetic induction devices had little use due to the necessarily loose coupling between the primary and secondary coils which-not only severely limited the range of operation and caused a large power loss, but made it necessary for the driver of the car to painstakingly orient the car so that the primary coil in the car would be positioned directly over the secondary coil buried in the driveway.

A supersonic .sound system operates at a frequency near enough to audio frequencies that it is'very difficult to-discriminate against the audio frequenciesand spurious operation will be encountered. Furthermore, .there are many devices (such as Whistles for calling .dogs) that operate .in the supersonic range and will .cause unwanted opening and closing of the garage doors.

Audio sound devices havethe same faults as supersonic devices to a greater degree as well as presenting an objectionable noise.

A photo-cell device is relatively dependable in operation but requires that a light beam be aimed at aphotocell across the driveway. Besides the necessity of an original adjustment, both the light source and the photocell are easily misaligned by accidental bumps. A greater objection 'is that a photo-cell device is non-selective and will respond to anything interrupting the light beam and will thus cause the garage door to open or close at frequent undesired times. Children particularly enjoy operating photo-cell devices and many :children are so inquisitive or wanton as to damage the equipment. Furthermore, it is easy for thieves to open the garage door to remove the car or other articles.

The present invention contemplates the use of inductive coupling between a tuned circuit in .a transmitter and an electrostatically shielded frame antenna associated with .a receiver'which operates a relay which may be tuned. The relay then closesa circuit which causes the Patented Nov. 30., 1954 door to open or close. Asthe induction field-is strong at low frequencies this deviceis particularly adaptable to the region of approximately -300 kilocycles per second. This low frequency range along with the lack of a radiation field and the lack of necessity for regeneration or heterodyning at the receiver and the short period of operation obviates the difficulties of complying with Federal Communications Commission regulations. The induction field strength is inversely proportional to the cube of the distance, and the area of operation is thus limited to a desirable size and is clearly defined.

It is, therefore, an object of the present invention-to provide an inductively coupled remote control device for opening a garage door from a remote point.

It is a further object of this invention to provide .such a device as nearly as possible free from spurious operation and which does not operate improper doors norcause communication interference.

A still further object of this invention is to provide such a remote control device having a relatively small, well-defined area of operation.

Another object of the present invention is to provide such a device which is not operable by unauthorized persons and which is tamper-proof.

A further object of the present invention is the provision of a remote control device having a modulated frequency and having a resonant relay and time delay network to prevent spurious operation in response to natural or man-made interference signals.

Still further objects of the present invention will become readily apparent through the following description with reference to the accompanying drawings in which:

Figure 1 is a schematic view of a preferred form of the receiver;

Figure 2 is a schematic diagram of one form of'the associated transmitter; and

Figure 3 is a schematic diagram of amodified receiver including a time delay network and resonant relay.

The transmitter shown includes a conventional oscillator which is powered by an automobile battery and a vibrator unit. As the power supply is not smoothed, the oscillator frequency will be modulated by the frequency of the vibrator. Modulation may, of course, be obtained by other means such as vibratingreeds which are well adapted to low audio frequencies. The electrostatically shielded frame antenna of the receiver is relatively insensitive to electric field interference'and picks up only the induction field signal from the transmitter. This signal is amplified by tuned circuits responsive only to the transmitter frequency and then detected. The 'modulating signal thus detected is amplified and detected to operate a relay which may control the opening or closing of garage doors or such other operations as may be desirable.

The system as outlined above is very nearly fool-proof, but to render it even more perfect an operation, we-have found that a tuned relay is desirable. It is desirable that the relay should not be tuned to a fundamental or harmonic frequency of commercial power lines as spurious operation could be introduced thereby under some circumstances. 90 cycles is suggested for this frequency, as it is well within the operating range'of amechanical vibrator, such as that used in the preferred form of the transmitter, and is well removed from the fundamental and harmonics of commercialpower'line frequencies, such as the usual cycles per second and the sometimes encountered 25 cycles per second. As steep interferences, such as lighting discharges or industrialinterference, may contain cycle per second components, we have found it desirable to includea timedelay network in conjunction with the tuned relay so that the modulating oscillations must continue for approximately one second before the control relay will respond. This time delay is sufficient to preclude operation by ,any'non-corm petitive signal, such as the components found in a steep wave front interfering signal, and is short enough to prevent any undesirable delay in the operation .of a garage door or the like.

The receiver as shown in Figure 1 comprises a power supply, comprising a transformer the primary .of which is connected through a fuse 3 to a.source of alternating current '5. A secondary winding 7 is grounded at one end 9 and at the other end 11 is connected to one side of the filament of each of the tubes in the receiver, the other side of each filament being, of course, grounded. Another secondary winding has its extremities connected to the plates 13 and 15 of a full-wave rectifier which may be a type 6X5. A center tap 17 of this winding is connected to ground through resistors 19, 21 and 23 in parallel with resistor 25. The cathode 27 of the rectifier is connected to one side of capacitor 29, the other side of this capacitor being connected to the junction point of resistors 19 and 25. The cathode 27 is also connected to one side of capictor 31 and constitutes the B+ supply. The other side of this capacitor is grounded.

The frame antenna 33 is shielded by a grounded electrostatic shield 35 comprising a grounded conductor completely surrounding the antenna 33. The potential induced in the antenna 33 is applied to a tuned circuit 37 which comprises three inductors, 39, 41 and 43, and

a capacitor 45 which is connected across inductor 41, said inductor being variable for tuning the antenna circuit. The signal is then induced in a tuned circuit 47 which is tunable by means of inductance 49. This signal is applied to the control grid of a radio frequency amplifier tube 51 which may be a type 6BA6. Tap 22 on resistor 21 provides grid bias through resistor 48 for the control grid of tube 51. The plate voltage of tube 51 is supplied by the B+ supply obtained through a resistor 53 and the tuned circuit 55.

The amplified signal from tube 51 is imparted by tuned circuits 55 and 57 to the control grid of a radio frequency amplifier tube 59 which may be a 6BA6. The control grid bias of tube 59 is obtained through resistor 61 from tap 22. A large capacitor is connected between tap 22 and ground to remove any fluctuations from the grid bias of tubes 51 and 59. The plate voltage of tube 59 is supplied by the B] supply obtained through a resistor 62 and the tuned circuit 63.

The amplified signal from tube 69 is induced by tuned circuits 63 and 65 to the diode plates 67 of a detector amplifier tube 69 which may be a 6AT6 where the modulating audio frequency signal is detected. This audio signal is applied to the control grid 71 of tube 69 by means of coupling capacitor 73 and a filter network consisting of two resistors 75 and 77 and a capacitor 79. The triode plate voltage of tube 69 is obtained through a resistor 81 from the B+ supply. The amplified audio signal from the triode plate of tube 69 is applied through capacitor 83 to a control grid 85 of one section of a twin triode amplifier tube 87 which may be a 6SN7.

The cathode 89 of this triode section is biased by means of the cathode resistor 91 and capacitor 93. The voltage on the plate 95 of this triode section is supplied through resistor 97 from the 3-}- supply. The amplified audio signal from the plate 95 of this section is applied by means of a capacitor 99 to the grid 101 of the other section of the tube 87. The grid 101, cathode 103 and plate 105 of this triode section act as an anode bend detector. The bias of grid 101 is obtained through a resistor 107 from the junction of resistors 19 and 21. The signal detected by the anode bend detector appears as a fluctuating direct current voltage across the inductance 109 which is paralleled by a capictor 111 and relay 113 is thereby closed to actuate the mechanism to close or open a garage door. The inductance 109 and the capacitor 111 may form a resonant circuit.

Two capacitors 32 and 34 connect the input tuned circuit 37 to the voltage supply source 5 so that a signal may be applied through the supply lines rather than by inductive coupling of the transmitter and the antenna 33.

The transmitter shown in Figure 2 is powered by a six volt automobile battery (not shown) and a vibrator 115. The fixed end of the vibrating contact 117 is grounded through a radio frequency choke 119. The fingers 121 contacting the vibrating contact are connected to the extremities of the primary winding 123 of a transformer 125. A center tap 126 on the primary winding 123 is connected through a switch 127 to the ungrounded side of the automobile battery. The secondary winding 129 of the transformer is connected across a capacitor 131 and is grounded at one end. The ,other end is connected through a radio frequency choke 133 to an oscillator 135. This oscillator may be of any desired type although for purposes of illustration one of the Colpitts type is shown. The oscillator 135 is of 4 the well known self-rectifying type, and the radio frequency signal generated by the oscillator is thus modulated by the fluctuating plate supply voltage, the frequency of which is of course the same as the frequency of the vibrator. No conventional transmitting antenna is provided so the radiation field is negligible. The inductance field from the inductance 137 of the tank circuit of the oscillator, is, however, considerable. In fact, the use of applicants coil as an antenna has been found to give the highest possible ratio of inductance field to radiation field.

An improved form of receiver embodying a tuned relay and a time delay network is shown in Figure 3. A shielded loop or frame antenna 139 similar in function to the antenna 33 is used to receive the signals from the transmitter which are then applied by means of an antenna matching transformer 141 to the control grid 143 of a radio frequency amplifier tube 145. The amplified signals are fed from the tube 145 by means of a radio frequency transformer 147 to the control grid 149 of a second radio frequency amplifier tube 151 and from there through a second radio frequency transformer 153 to the diode plate 155 of a tube 157 which may contain a triode amplifier within the same envelope. The diode section of the tube 157 along with a network comprising capacitors 159 and 161, resistor 171 and potentiometer 173 comprises the radio frequency demoduator.

The audio frequency signal derived from the demodulator is taken from the movable tap on the potentiometer 173 which serves as a sensitivity control, from whence it is applied to the control grid 175 of an audio frequency amplifier tube which as heretofore noted may be contained in the same envelope as the tube 157. The audio frequency signal is then applied to the control grid 177 of an electron tube 179 arranged in a cathode follower circuit including resistors 181, 182 and 184 to match the high impedance of the previous amplifier stage to the relatively low impedance of the coil 183 of a resonant relay 185. The contacts 187 of the resonant relay which are contacted by the armature 189 are grounded through a resistor 191 of relatively low value which, for illustrative purposes, may be of the order of 3,000 ohms. The armature 189 is coupled through a time delay network including resistor 193 of very high value compared with resistor 191 and capacitors 195 and 197, to the control grid 199 of a control tube 201. For purposes of illustration, the value of resistor 193 may be of the order of 6 or 7 megohms and capacitors 195 and 197 of the order of .05 microfarad. The coil 203 of a control relay 205 is included in the plate circuit of the control tube 201 and is parallelled by an electrolytic capacitor 204 of the order of 50 microfarads. The contacts 209 of the control relay 205 are normally open and are closed by plate current of the control tube 201 passing through the relay coil 203.

Power for the receiver is supplied through A. C. lines 211 to the primary of a power transformer 213. center tapped secondary is provided on the transformer 213, which in conjunction with a full wave rectifier tube 215, supplies D. C. potential to a filter network com prising capacitors 217 and 219 and resistor 221. Plate potential is supplied from this filter network to the tubes 145, 151, 157, 179 and 201, and biasing potential is supplied from this network through a resistor 223 to the armature 189. The resistor 223 is of a high value, being about 1,000 times the value of resistor 191, or for illustrative purposes, of the order of 3 megohms. A filament winding is also provided on the transformer 213 to provide filament current for all of the tubes in a conventional manner.

The potential applied through the resistor 223 to the armature 189 is also applied through the resistor 193 to the control grid 199 of the tube 201 to render the tube normally non-conductive when in cut-off position. Capacitors 195 and 197 are of course charged to this biasing potential. When the resonant relay is excited by the proper frequency, contact is established between the armature 189 and one of the contacts 187. This causes the capacitor 197 to discharge practically instantaneously through the resistor 191 to ground. The resistor 191 is included to protect the armature 189 and contacts 187 from being burned by heavy discharge cursistor 223 in the charging circuit. During the time in which the armature 189 contacts one of the contacts 187, the capacitor 195 discharges comparatively slowly through the resistor 193. As the resistor 193 is of high value, the discharge time for capacitor 195 is long compared to the discharge time for capacitor 197, and consequently the biasing voltage applied to the grid 199 of control tube 201 decays comparatively slowly. The armature 189 contacts one of the contacts 187 only about 20% of the time when the relay 185 is energized by current of the proper frequency. This is sufiicient time to completely discharge the capacitor 197, and the capacitor 195 continues to discharge during the 80% of the time when no contact is made by partially recharging the capacitor 197. The values given as illustrative for resistor 193 and capacitor 195 are of such order that the bias on the grid 199 of the control tube 201 will not fall to a sufliciently low value to cause operation of the control relay 205 for a period of about one second or until the vibrating armature 189 has completed about 90 oscillations when 90 cycles has been chosen as a modulating frequency. Thus random fluctuations of the armature 189 of relay 185 caused by non-repetitive disturbances cannot cause operation of the control relay 205. Closing of the contacts 209 of control relay 205 may energize a motor to open and close a garage door, and further control of this motor is not within the scope of this invention.

From the foregoing it is apparent to those skilled in the art that a superior apparatus is here provided for the remote control of a garage door or the like, said apparatus relying on inductive coupling and not being susceptible to tampering or spurious operation.

Although certain specific embodiments of the present invention have been shown and described, it is to be understood that further modifications including the use of vibrating reeds for modulating the transmitter may be made without departing from the spirit and scope of the appended claims.

We claim:

1. A radio receiver for a remote radio controlled garage door operator responsive to actuate the door operator when there is applied thereto the induction field of a selected radio frequency carrier wave having a frequency of substantially 50,000 to 500,000 cycles per second and modulated by an audio frequency of substantially ninety cycles per second comprising an electrostatically shielded antenna, a radio frequency amplifier, a coupling circuit tuned to the frequency of the carrier wave coupling said antenna to said amplifier, a demodulator for separating the audio frequency from the carrier wave, means for coupling the output of said amplifier to said detector, an audio frequency amplifier connected to the output of said demodulator for amplifying the audio frequency, a tuned relay connected to the output of said audio frequency amplifier and tuned to a fre quency of substantially ninety cycles per second, a time delay means connected to the contacts of said tuned relay, and a relay for operating the door actuator connected to the output of said time delay means, said time delay means having a delay of approximately one second so that said door operating relay operates after said tuned relay operates substantially continuously for at least one second.

2. A radio receiver as set forth in claim 1 wherein a cathode follower circuit is connected between the audio frequency amplifier and the tuned relay to match the impedances of the audio frequency amplifier and the tuned relay, and the time delay means includes a RC time delay network connected to the contacts of the tuned relay and an electronic tube having a cathode and control grid and anode, said anode being connected to the door operating relay to cause operation thereof when said electronic tube conducts a predetermined amount, said control grid being connected at a point in said RC network biasing said electronic tube so that the conduction thereof normally is not sufficient to actuate said door operating relay, the bias on said control grid being removed and permitting conduction of said electronic tube after the tuned relay operates substantially continuously for one second.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,555,893 Thompson Oct. 6, 1925 1,685,480 Clark Sept. 25, 1928 1,760,479 Coleman May 27, 1930 1,786,610 Hammond Dec. 30, 1930 1,872,372 Wensley Aug. 16, 1932 2,004,460 Brockstedt June 11, 1935 2,064,639 Whitelock Dec. 15, 1936 2,069,860 Stewart Feb. 9, 1937 2,118,930 Lilja May 31, 1938 2,122,145 Kear June 28, 1938 2,139,157 Giradin Dec. 6, 1938 2,188,991 Wintsch Feb. 6, 1940 2,361,653 Roberts Oct. 31, 1944 FOREIGN PATENTS Number Country Date 261,384 Great Britain Oct. 6, 1927 857,895 France Oct. 3, 1940 653,875 Germany Apr. 28, 1929 OTHER REFERENCES Raft Radio, p. 241, Wireless World, May 1940.

Radar Electronic Fundamentals, Navships 900,016. 

